This invention concerns a rotation-angle sensor for displaying a plurality of rotations of a shaft using a geared-down drive and a potentiometer unit whose resistance-adjustment angle is smaller than one complete revolution, with a coupling from a rotation-angle-sensor housing to outside a component cover being formed by flexible leads. Such a sensor can be used, for example, for displaying wear of brakes for street vehicles.
With increasing safety demands for street vehicles, in conjunction with increased use of electronics, function monitoring with sensors of machinery requiring safety, such as wheel brakes, is increasingly becoming mandatory.
The manner in which brakes operate is that an operation force is applied via a lever which is transmitted via a threaded spindle to thrust against a brake lining. An automatic wear adjuster, which is integrated with the threaded spindle, compensates for the resulting lining and disk wear by screwing the threaded spindle outwardly. The threaded-spindle rotations are used to indirectly read the wear by use of a rotation-angle sensor.
The sensor continually monitors wear of the lining and disk layer throughout a predetermined wear lifetime, there being, at each possible operation and maintenance condition of a brake, a definite relationship between wear and a signal value of the sensor.
In this regard, during the lifetime, that is until the brake lining is worn away, the threaded spindle goes through about ten revolutions, which requires a "gearing down" mechanism, because normally a rotation potentiometer is maximally operative through only one revolution. Thus, in order to achieve an accurate indication of brake wear: firstly, an exact alignment of a shaft of the rotation-angle sensor, which includes the potentiometer, to the threaded spindle is necessary; and, secondly an exact alignment of a rotation-angle-sensor housing itself to the rotation spindle, or a component in which it is mounted, is necessary because a flawed arrangement could magnify a mistake by a factor of ten in a displayed resistance value.
Accordingly, it is an object of this invention to provide an apparatus which allows extremely exact relationships of shafts to one another and of a rotation-angle housing to a monitored component shaft, and further which allows simplified maintenance because the component, with the component shaft, and the rotation-angle sensor can be dismounted and mounted without being relatively adjusted to one another.